The invention is related to Internet protocol (IP) telephony systems that provide telephony services to mobile telephony devices. The mobile telephony devices communicate with the IP telephony systems via data packet communications that are transmitted over a wireless data connection.
A mobile telephony device runs a software application provided by an IP telephony system. The software application enables the mobile telephony device to place or receive voice over Internet protocol (VOIP) telephone calls through the IP telephony system. The software application can also enable the mobile telephony device to send and receive other forms of telephony communications, such as SMS and MMS messages, video calls, and other similar communications. The software application may also enable the mobile telephony device to obtain and play voicemail messages that have been recorded for the user of the mobile telephony device.
When an application provided by an IP telephony system is loaded and run on a mobile telephony device, the application contacts and registers with the IP telephony system via a wireless data connection provided by the mobile telephony device. So long as the application is actively running on the mobile telephony device, a wireless communication path may be kept open between the application on the mobile telephony device and the IP telephony system. However, keeping such a communication path open and available may require that a small amount of data traffic be sent between the mobile telephony device and the IP telephony system on a periodic basis. These periodic messages are called “keep alive” messages.
Provided the communication path remains open and available, any time that an incoming call for the mobile telephony device is received by the IP telephony system, the call is connected to the mobile telephony device via that open path. Likewise, if an incoming SMS or MMS message directed to the mobile telephony device is received by the IP telephony system, the communication is delivered to the mobile telephony device via that path. Also, if the user of the mobile telephony device wishes to place an outgoing call, or send an outgoing SMS or MMS message, the communication is established or sent via the open path.
Because most mobile telephony devices run on battery power, it is common for a mobile telephony device, or the application, to cease sending “keep-alive” messages, and thus terminate the open path, if no activity occurs for an extended period of time. Doing so reduces power consumption, and extends battery life. Also, a user may not open and run such the software application used to communicate with the IP telephony system until the user wishes to place an outgoing call or send an outgoing message. Further, if a user has ended a call, or sent a communication, the user may choose to deliberately terminate such an application. If the application is not running on the mobile telephony device, or if the wireless communication path is not open and available, it is difficult and sometimes impossible for the IP telephony system to readily communicate with the mobile telephony device for the purpose of terminating a call to the mobile telephony device, or delivering a message to the mobile telephony device. Moreover, when the IP telephony system is not capable of communicating with the application on the mobile telephony device, the IP telephony system is unable to even inform the user that the user has missed a call, or that communications and/or voicemail messages are waiting for the user.